Jitsu wa Imouto deshita.: Saikin Dekita Giri no Otouto no Kyorikan ga Yatara Chikai Wake

A little brother-like secret relationship with his little sister?! A romantic comedy between siblings with a misunderstanding begins!

Akira, my stepbrother, was brought into my life as a high school student after my parents remarried. He is a cute boy but shy because of the complicated family environment he grew up in. I had a crush on my brother, so I always spent time playing with Akira for his sake… He loves me… We hit it off, and the distance between us grew rapidly! I asked him,
"...Brother, do you like me by any chance?"
"Of course I do."
The misunderstanding between the two of us deepens. And finally, I realized that Akira was my "sister" and I was confused...
"I like the distance between my brother and me as we have always been. I'd rather be with you more than I am now."
Akira's approach to me, aiming to make us "lovers" instead of "siblings," has begun!
A flirtatious romantic comedy with a little sister who is too cute and carefree to be a brother!

https://www.cmoa.jp/title/287517/